fix: Remove malformed header markup and duplicate debugger toggle button

[akash3911]

Summary

This PR fixes malformed toolbar markup in index.html caused by:

• Duplicate id="btn-debugger-toggle" elements
• An unclosed <button> tag
• Nested toolbar buttons inside malformed markup

Changes Made

• Removed the incomplete debugger toggle button
• Kept only a single valid btn-debugger-toggle element
• Properly closed toolbar button tags
• Restored correct toolbar hierarchy inside .header-right

Result

• Eliminates duplicate DOM IDs
• Fixes invalid nested button structure
• Improves debugger toggle event binding reliability
• Prevents inconsistent browser DOM auto-repair behavior
• Improves toolbar accessibility and maintainability

Verification

Verified that:

document.querySelectorAll('#btn-debugger-toggle').length

now returns:

1

Issue

Closes #73

[siddu-k]

@akash3911 has conflicts that must be resolved

[akash3911]

@siddu-k once check